You only need to that the first time. Once you have it set up it's just as fast and way cheaper for both merchants and buyers. There are plenty of payment services that take a percentage cut, Dwolla is the only one that doesn't.
The solution is to log out. For those of you who like being signed into Gmail put "accounts.youtube.com" in your adblock filters. That will prevent Google from automatically signing you in to Youtube and other services.